here’s a take on the histogram vs light meter debate via ‘digital imaging expert’ tim grey of microsoft fame. this was from his near daily q+a posting with readers.

One of the most useful advances of digital photography is the histogram. If one still uses film, say in large format photography, a histogram is available only after the film has been scanned. Is there a light meter that produces a histogram that would be useful in large format photography?

Tim’s Answer:

I completely agree with you that the histogram is incredibly valuable, which is why I’m including an in-depth article about histograms in the upcoming issue of my print publication, Digital Darkroom Quarterly. Histograms provide extensive information about the exposure in an image, and are valuable for evaluating that exposure for a given image, or for evaluating what an optimal exposure would be for a given scene.

Light meters, on the other hand, simply measure a specific luminance value. That value is averaged for the field of view being observed by the light meter. This is useful for determining appropriate exposure settings, but it is only based on a single luminance value. This is very similar to using the meter in your digital camera in order to evaluate the light levels in the scene you’re going to photograph.

As you’ve no doubt realized when using the meter in your camera, you can get very different results depending on where you point your camera (and depending on what metering mode you use). This is the limitation of a light meter. A histogram, on the other hand, shows you the range of tonal values present in a scene in a relative sense (by indicating the relative number of pixels at each luminance value in the scene captured in a given digital image).

So, to answer your question, no, there isn’t a light meter that will provide you with a histogram for large format photography. You can view a histogram of the scanned image (which is affected by the scan settings, obviously, and thus not necessarily a completely accurate histogram relative to what was present in the original capture), but there isn’t a light meter that will perform as you’re hoping.

However, you most certainly could use another digital camera to give you a good sense of what a histogram would look like for a given scene you plan to photograph with film using a large format camera. There are certainly many variables here to create challenges for you, but if you could frame the scene on a digital camera exactly as you will frame it for the large format film capture and then capture the image digitally, you could get a pretty good sense of the exposure situation. Obviously you would need to apply appropriate compensations based on the behavior of the film and the desire to maintain density with film rather than the brightest possible exposure without clipping for digital, but the point is that you could use a digital camera to provide you with a much better sense of what to expect within the scene you’re photographing, which can help guide your exposure decisions.